I know for a lot of people new to cosplay, or costuming in general, it can seem very intimidating. Well here is some advice- don't let what other people think of you effect your fun.
No matter where you go, how much time you spend on your costumes, if you bought them or made them yourself- someone will ALWAYS have something negative to say. Just shrug it off and go on. Don't let it bother you and try your best to maintain composure. If you feel someone said something really inappropriate about you or your costume, talk to them about it. Don't cuss at them or be rude back, simply tell them you felt their rudeness was uncalled for.
Oh, and the internet does not count. You should NEVER let something someone said about you on the internet bother you. It's just some person behind their computer.
And there is a difference between someone being rude and someone trying to give you constructive criticism. Don't get your undies in a bunch if someone says something to you like, "I can see you worked hard on this. Maybe next time you should try to do "x" thing to improve it." They may really only be trying to help. It's way different from someone saying "Omg your costume sucks."
All in all, what matters is how you feel about the costume, and not what others feel. So keep up all the hard work!